Building block



FIG. 1 is a perspective top view of a building block showing my new design;

FIG. 2 is a perspective bottom view of the building block, as shown in FIG. 1;

FIG. 3 is an enlarged front elevational view of the building block, as shown in FIG. 1;

FIG. 4 is a right-hand side elevational view of the building block, as shown in FIG. 3; and

FIG. 5 is a left-hand side elevational view of the building block, as shown in FIG. 3. 

The ornamental design for a building block, as shown. 